I upgraded SMSME from 7.9.1.51 to 7.10.0.17. After that antispam did not work and Content filtering also. After troubleshooting a bit I found that because upgrade was from 7.9 to 7.10 some folder and DCOM permissions were not correct. I fixed them but Content filtering still did not work. Or kind of worked. If I sent e-mail from outside with attachment which must have been quarantined and attachment removed I got e-mail with the file intact and couple minutes later notification that SMSME quarantined file from SMTP. After more troubleshooting I found that Microsoft Transport Service wanted the Read/Write access to the registry key SOFTWARE\Symantec\SMSMSE\7.10\Server\Components\SMTP
When I gave the Network Service Full Control to that key then Content Filtering started to work again. I did not find any mentions about that kind of permission is needed when I searched KB articles. Is there any info about that somewhere an I missed it?